Uptake of the measles, mumps and rubella vaccine in England has fallen yet again, official figures show.
Experts say MMR is the best way to protect children
Statistics for April 2003 to March 2004 showed 80% of two-year-olds had been given the MMR jab, down from 82% in 2002 to 2003.
The figures show that in south-east London, just 62% have had the immunisation.
The World Health Organisation says 95% of toddlers should have the jab to protect against the diseases.
The figures are also well below a peak of 92% coverage seen in 1995-96, before controversial research claimed the MMR jab was linked to autism.
However, information on the use of single vaccines is not collected, so more parents could be seeking separate mumps, measles and rubella vaccinations for their children.
Blame for the fall in uptake of the vaccine has been linked to fears raised about the safety of the jab.
In the late 1990s, some scientists suggested MMR might be linked to autism and bowel disease.
However, no research has ever proved a link, and the overwhelming majority of experts believe the vaccine is safe.
The latest large-scale study, published earlier this month in the Lancet, concluded that there was no evidence to support a link between the combined vaccine and autism in children.
Outbreaks of measles have already been seen in areas of the UK, such as south London, with very low uptake of the vaccine.
Public Health Minister Melanie Johnson backed MMR as the best form of protection against measles, mumps and rubella.
She said: "This annual data shows that eight out of 10 children aged two had received their MMR and more recent data from the Health Protection Agency shows that MMR uptake has increased in three of the four last quarters, which is encouraging.
"A recent major study of UK children concluded that children who receive the MMR vaccine have no increased risk of autism than children who don't have the
"This is consistent with numerous other studies from the UK and around the world.
"MMR is recognised by the World Health Organization as having an outstanding safety record."
Miss Johnson added: "Our overwhelming aim is for parents to have their children immunised with MMR, for them to be confident that this is the right thing to do, and to provide parents and health professionals with access to clear factual information about the vaccine."
Shadow Health Secretary Andrew Lansley said: "We deeply regret the fact that these MMR rates aren't higher and that in parts of the country coverage falls well below the level required for herd immunity.
"It is therefore a matter of urgency for public confidence to be restored.
"In our view that is not only about giving maximum attention to the studies which highlight the safety of the MMR vaccination, but the National Institute for Clinical Excellence should have an immediate responsibility to investigate the clinical effectiveness and appropriateness of the use of single vaccines."
The NHS Immunisation Statistics report also showed uptake of the meningitis C vaccine increased from 92% to 93% last year.
In addition, 94% of youngsters had been immunised against diphtheria, tetanus and polio, and 93% were immunised against whooping cough and Hib - both
similar percentages to the previous years.
The percentage of over-65s getting the flu jab increased to 71% - up from 69% in 2002/03.